Nanoparticles have unique properties that have been exploited to deliver DNA to specific animal cells. It has been found that when certain DNA-coated nanoparticles are incubated with cells not having a cell wall, the cells take up the nanoparticles and begin expressing genes encoded on the DNA. Semi-conductor nanoparticles (e.g., quantum dots (“QDs”)) within the size range of 3-5 nm have also been used as carriers to deliver molecules into cells. DNA and proteins can be linked to certain ligands attached to the QD surface. See e.g., Patolsky, et al. (2003) J. Am. Chem. Soc. 125:13918. Carboxylic acid- or amine-coated QDs can be cross-linked to molecules containing a thiol group, see, e.g., Dubertret et al. (2002) Science 298:1759; Akerman, et al. (2002) Proc. Natl. Acad. Sci. U.S.A. 99:12617; Mitchell, et al. (1999) J. Am. Chem. Soc. 121:8122, or an N-hydroxysuccinimyl (“NHS”) ester group, by using standard bioconjugation protocols. See, e.g., Pinaud, et al. (2004) J. Am. Chem. Soc. 126:6115; Bruchez, et al. (1998) Science 281:2013. An alternative way to attach molecules to the surface of QDs is via conjugation of streptavidin-coated QDs to biotinylated proteins, oligonucleotides, or antibodies. See, e.g., Dahan, et al. (2003) Science 302:442; Pinaud, et al. (2004) J. Am. Chem. Soc. 126:6115; Wu, et al. (2003) Nature Biotechnol. 21:41; Jaiswal, et al. (2003) Nature Biotechnol. 21:47; and Mansson, et al. (2004) Biochem. Biophys. Res. Commun. 314:529.
Delivery of foreign nucleic acid molecules to plants is challenging due to the presence of plant cell walls. Current methods rely on invasive delivery for genetic transformation of plants. In plant cells, the cell wall is a barrier against the delivery of exogenously applied molecules. Many invasive cell delivery methods, for example, biolisitic delivery (gene gun), microinjection, electroporation, and Agrobacterium-mediated transformation, have been employed to achieve gene and small molecule delivery into walled plant cells, but delivery of proteins has only been achieved by microinjection. Where nanoparticle delivery of nucleic acid molecules to plant cells is desired, the cell wall is removed before the addition of the particles to protoplasts of plant. See, for example, Torney, et al. (2007) Nature Nanotechnol. 2:295-300.